Conventionally, there has been known a signal processing device that transmits and receives signals to and from an external signal transmission/reception unit without contact. The signal processing device has a signal transmission/reception coil instead of a signal terminal in a general signal processing device. Signals are transmitted and received by inductive coupling between the signal transmission/reception coil in the signal processing device and the signal transmission/reception coil in the external signal transmission/reception unit without contact. The signal transmission/reception device is described in Patent Document 1 or Patent Document 2.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2010-103611
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2011-66515